KR101492864B1 - Food packing material generating plasma - Google Patents

Abstract

The present invention relates to a food packing material capable of generating plasma and, more specifically, to a food packing material capable of generating atmospheric plasma, composed of an outer layer of the packing material, a first electrode layer, a dielectric barrier layer and a second electrode layer and applying voltage to the first electrode layer to generate the atmospheric plasma. The present invention may sterilize microorganism without damage to the packing material which may occur in a distribution process since the plasma may be generated by using a structure of a packing container itself and may expect various effects of food poisoning during distribution, extension of expiration date, saving of additional food sterilization costs and distribution costs, etc.

Description

[0001] Food packaging material generating plasma [0002]

The present invention relates to a food packaging material capable of generating a plasma, and more particularly, to a food packaging material capable of generating a plasma, and more particularly, to a method of manufacturing a food packaging material capable of generating a plasma by generating an atmospheric plasma by applying a voltage to the first electrode layer, To a food packaging material capable of generating an atmospheric plasma.

In general, foods, beverages, etc. are packed and delivered to consumers in order to increase the value of the products and to protect the goods during the distribution process. In the case of dry food, plastic packaging containers such as PET (polyethylene terephthalate) are used to prevent moisture absorption, discoloration, fat burning and flavor degradation, and moisture and oxygen permeability And an aluminum foil having a low barrier property is further laminated. In addition, it is possible to reduce the growth rate of microorganisms, retard the degradation by enzymes, and maintain the color of meat by applying the gas replacement packaging method developed as an improvement measure for the vacuum packaging method. However, microorganisms can grow even if packaged food is used. In addition, since pasteurization treatment is performed before packaging except for high pressure high temperature sterilization using a retort pouch to sterilize food, re-contamination (cross contamination) is likely to occur at this time A problem may occur during storage. Heat sterilization is considered to be effective and safe, but it has disadvantages due to physicochemical changes of food such as destruction of nutrients and change of flavor caused by heat sterilization. In addition, heat sterilization can not be applied to the treatment of heat sensitive foods. In recent years, non-thermal sterilization methods have been developed and commercialized in order to overcome the disadvantages of the heat sterilization. Examples thereof include ultra violet (UV), radiation (gamma ray, electron beam, X-ray), and ultra high pressure process. Ultraviolet rays are weak in permeability, making it difficult to treat food inside the package. On the other hand, radiation has high permeability, so it can be processed in a fully packaged state, but commercialization is slowing because of initial installation cost, management cost, and low acceptance of consumers. In case of ultra high pressure process, it is possible to treat in a fully packaged state, but this method also has a problem that initial investment cost is high and also physicochemical change of food is caused.

Atmospheric pressure cold plasma is the solution proposed as an alternative to the non-heat sterilization technology of such packaged foods. Plasma is very economical, easy to move, and easy to work, compared with other non-heating methods. However, it is difficult to sterilize the food inside the package with the plasma generated from the outside because the permeation power of the atmospheric pressure low-temperature plasma is low. However, if the plasma is generated inside the package, it will be possible to sterilize effectively. (Rød SK et al., 2012, Food Microbiol. 30, 233-A), which causes a dielectric barrier discharge (DBD) using an external electrode capable of applying a voltage by replacing helium or argon gas 238). In this case, additional equipment consisting of electrodes in addition to the packaging material is required, and it is difficult to handle curved food, and the effect is limited for very thick food. (RNS) and reactive oxygen species (ROS) in plasma using nitrogen or oxygen gas rather than the sterilization effect of atmospheric plasma using helium gas. In the case of oxygen gas, there is a problem that the plasma formation is very difficult because the plasma discharge breakdown voltage is higher than the helium gas. Also, if the shape of the packaging material is not flat, it is difficult to generate a plasma and it is difficult to expect a certain sterilization result because it is highly uneven.

Therefore, it is necessary to develop a plasma generation device using the structure of the packaging container itself, and it is necessary to develop atmospheric plasma generation which is excellent in sterilization effect using nitrogen gas or atmospheric air used for food packaging.

Accordingly, the present inventors have repeatedly studied to develop a technology useful for inhibiting microorganisms that may occur during the distribution process without damaging the packaging material and sterilizing the packaging material itself. As a result, not only in the factory but also in retailers and general consumers The present invention has been completed as a packaging material which can sterilize by using atmospheric pressure plasma immediately before opening the package.

Accordingly, it is an object of the present invention to provide a food packaging material capable of generating a plasma capable of sterilization by itself only by a packaging material, and capable of sterilization at low temperature, without the need for an additional device.

In order to achieve the above object, the present invention provides a packaging material outer layer formed of a synthetic resin film; A first electrode layer of an electroconductive metal thin film laminated on the outer layer; A dielectric barrier layer stacked on the first electrode layer and being an insulator; And a second electrode layer of an electrically conductive metal foil laminated on the dielectric barrier layer and perforated at regular intervals so that a dielectric barrier layer is visible, wherein the second electrode layer is used as a ground electrode and a voltage is applied to the first electrode layer And atmospheric pressure plasma is generated by applying atmospheric pressure plasma.

In the present invention, the electrode layer to which the voltage is applied may use both the first and second electrode layers. The first electrode layer may be used as a ground electrode and the atmospheric plasma may be generated by applying a voltage to the second electrode layer.

In an exemplary embodiment of the present invention, an electrode protection layer may be formed between the first electrode layer and the dielectric barrier layer and formed of a synthetic resin film.

In one embodiment of the present invention, the electrically conductive metal may be selected from the group consisting of aluminum, iron, nickel, chromium, copper, silver and gold.

In one embodiment of the present invention, the insulator may be selected from the group consisting of polytetrafluoroethylene, mica, polyethylene, polystyrene, and polyester.

In one embodiment of the present invention, the voltage applied to the first electrode layer may be a low frequency voltage of 1 to 100 kHz.

In an embodiment of the present invention, the packaging material is characterized by exhibiting a sterilizing effect on food poisoning bacteria.

In one embodiment of the present invention, the food poisoning bacterium is Listeria monocytogenes, E. coli, Salmonella typhimurium or Aspergillus flavus.

When the food packaging material according to the present invention is applied to processed foods or foods having a long distribution process, it is possible to suppress the microorganisms that may occur during the distribution process without damaging the packaging materials, and to apply the packaging materials themselves to sterilization, It can be expected to have various effects such as safety improvement such as prevention of danger, prolongation of shelf life, additional food sterilization cost, and reduction of distribution cost. In addition, it will be possible to provide more reliable food as soon as packaging, as well as retailers and general consumers, can have sterilization using atmospheric plasma immediately before opening the package if there is a simple power supply.

1 is a basic structure of a food packaging sheet according to the present invention.
FIG. 2 is a schematic view illustrating a plasma sterilization process of the food packaging material according to the present invention.
3 is a schematic view of a multilayer sheet structure fabricated to test the plasma treatment of a food packaging material according to the present invention.
FIG. 4 is a photograph of a plasma discharge generated inside a bag in which a food packaging material according to the present invention is actually implemented.
FIG. 5 is a graph showing the killing effect of Listeria monocytogenes by plasma treatment using the food packaging material according to the present invention.
6 is a graph showing the killing effect of E. coli by plasma treatment using the food packaging material according to the present invention.
FIG. 7 is a graph showing the killing effect of Salmonella typhimurium by plasma treatment using the food packaging material according to the present invention.
FIG. 8 is a graph showing the killing effect of the Aspergillus plase booth by the plasma treatment using the food packaging material according to the present invention.

The present invention relates to a food packaging material capable of generating plasma. The inventors of the present invention have confirmed that the packaging material itself can be sterilized by itself only by using the packaging material without the need for an additional device, thereby completing the present invention.

Therefore,

A packaging material outer layer formed of a synthetic resin film;

A first electrode layer of an electroconductive metal thin film laminated on the outer layer;

A dielectric barrier layer stacked on the first electrode layer and being an insulator; And

And a second electrode layer of an electrically conductive metal foil laminated on the dielectric barrier layer and perforated at regular intervals so that a dielectric barrier layer is visible,

Wherein the second electrode layer is used as a ground electrode and a voltage is applied to the first electrode layer to generate an atmospheric pressure plasma.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

1 is a view showing a basic structure of a food packaging sheet according to the present invention.

1, the multilayer sheet 10 comprises an outer layer 11, a first electrode layer 12, an electrode protection layer 13, a dielectric barrier layer 14 and a second electrode layer 15. The packaging sheet of such a structure can perform self-sterilization of the packaged food by using the plasma generated inside the packaging material when only the external power source is connected without the need for an additional device because the packaging material itself is a plasma generating unit.

The electrode protection layer 13 may be replaced by the dielectric barrier layer 14 and may prevent the packaging material from contacting the package or prevent oxidation of the electrode and may be made of the same material as the outer layer 11 .

In recent years, packaging materials having various shapes have been made and used for various purposes. Therefore, the dielectric barrier discharge using the thin electrode layer and the dielectric barrier layer proposed in the present invention is not limited to the structure shown in FIG. 1, And a dielectric barrier layer may be added and applied.

As the first electrode layer 12 and the second electrode layer 15, aluminum conventionally used as a packaging metal layer may be used, and materials such as nickel, chromium, copper, silver, and gold having good electrical conductivity may be used. The first electrode layer 12, which also serves as an oxygen barrier layer, is preferably formed by uniformly laminating the first electrode layer 12 with a thickness of 100 to 200 μm and covering all the surfaces. On the other hand, the second electrode layer 15 contributing to plasma generation must be formed with a predetermined gap so that the dielectric barrier layer 14 can be seen. The shape of the second electrode layer 15 can be variously formed, such as a circle and a square. Area and sterilization power.

Insulators that can be used as the dielectric barrier layer 14 should be a material that can withstand a high voltage while maintaining a minimum thickness, and preferably an insulator such as Teflon, Mica, Polyethylene, Polystyrene, Polyester or the like may be used. The dielectric breakdown voltage is determined according to the dielectric strength value and the thickness of the selected material. If the voltage is roughly higher than the driving voltage of the atmospheric plasma, most of the materials can be used.

In addition, since the electrode thickness is not an important parameter in plasma generation, it is possible to use an electrode layer having a proper thickness that can be used for a packaging material. The thickness of the dielectric barrier layer may be thin enough not to cause dielectric breakdown, May be used.

FIG. 2 is a schematic view illustrating a plasma sterilization process of the food packaging material according to the present invention.

2, the dielectric barrier discharge 14 is mainly driven at a low frequency (1 to 100 kHz), and the waveform can be any of a sine wave, a square wave, a pulse, and the like. The peak voltage is driven within the dielectric breakdown voltage of the dielectric barrier used and is typically between 1 and 10 kV. When treating temperature sensitive growth, the gas temperature and the temperature of the electrode derived from the plasma are important. Using a pulse voltage having a pulse width of tens to hundreds of nanoseconds and a repetition rate of 1 to 100 kHz, .

The plasma used in the present invention is a dielectric barrier discharge. As the discharger, inert gas such as helium, argon and neon as well as oxygen, nitrogen and air can be used at normal pressure.

Also, the type of the substitution gas usable as the discharging body of the packing material plasma may vary depending on the packaged food, and usually nitrogen, oxygen, and carbon dioxide are used in many cases. It is preferable that at least 1% of oxygen or nitrogen gas is substituted because microorganism sterilization using atmospheric plasma plays an important role in sterilization of active nitrogen species and oxygen species. In the case of air, the composition ratio (N ₂ : O ₂ = 78.09: 20.95) is also easy to discharge the dielectric barrier and effectively sterilize without additional gas cost.

The synthetic resin used as a material of a general food packaging material may be used as the outer layer 11. The synthetic resin that can be used is not particularly limited as long as it is a synthetic resin composition for food packaging known in the art. For example, polyethylene, polystyrene, poly Propylene, polyvinyl chloride, and the like.

Hereinafter, the effects of the plasma packaging material according to the present invention will be described in detail with reference to the following experimental examples.

Experimental Example .

(1) Sample preparation

Commercially available cheeses were purchased and used in the experiments. For the inoculation test, the cheese was cut into a size of 15 × 15 × 2 mm and placed in a polyethylene bag (15 × 20 cm; Sunkyung Co. Ltd, Seoul, Korea) (model: ELV-8, 2.5 MeV, EB-Tech, Daejeon, Korea) to a total absorbed dose of 35 kGy.

(2) Inoculation of strain

The pathogenic bacteria used in the three kinds of experiments jeneseu L. monocytogenes (Listeria monocytogenes , KCTC 3569), Escherichia coli O157: H7 ( Escherichia coli O157: H7, ATCC 43889) and Salmonella Typhimurium, KCTC 1925), and one type of fungus is Aspergillus flavus , KCTC 6905) was used. Each microorganism was purchased from the Korean Collection for Type Cultures (KCTC) and used for the experiment.

In the case of bacterial activity,L. monocytogenes(Tryptic soy broth, Difco) and tryptic soy agar (Difco) supplemented with 0.6% yeast extract (Difco, Laboratories, Sparks, MD, USA)E. coli O157: H7 used TSB and TSA,S.Typhimurium was used nutrient broth and nutrient agar. The optimum culture temperature for each strain was 37 ℃. Three kinds of pathogenic microorganisms were inoculated in 25 mL of the active medium according to each strain, and cultured for 24 hours with shaking. One 0.1 mL of the culture solution was inoculated into 25 mL of fresh medium for 18 hours After the secondary culture, the culture was used for the experiment. The culture was centrifuged (2,090 × g, 10 min, 4 ℃) using a centrifuge (UNION 32R, Hanil Science Industrial Co., Ltd., Seoul, Korea) to reduce the error in the culture medium The supernatant was removed and washed twice with 0.85% sterile saline. The initial concentrations of the 3 strains used in the experiment were 10⁸-10⁹ CFU / mL, and the strain was inoculated into the culture medium and the sterilized sample, respectively.

A. flavus was inoculated on a PDA medium containing 10% citric acid (potato dextrose agar) and cultured at 25 ° C for 5 days. Then, using 5 mL of 0.1% Tween 80 solution sterilized in the spores formed, . This method was repeated 3 times, and the separated spore suspension was diluted and adjusted to 10 ⁵ spores / mL for the experiment.

(3) Plasma treatment

In order to test the plasma packaging material of the multilayer sheet structure of the present invention, a simple structure as shown in Fig. 3 was fabricated. In order to observe the atmospheric pressure plasma generated on the inner side of the packaging material, a packaging material having a transparent polyethylene terephthalate (PET) front side and a polypropylene (PP) side adsorbed on an aluminum foil is prepared Respectively. And the aluminum on the rear side was used as the first electrode layer. The thickness of each surface is 0.11 mm. A PTFE adhesive sheet (6331-10, Alpha Trading Co., Seoul, Korea) having a thickness of 0.28 mm was used as a dielectric barrier layer. Since Teflon has an insulation strength of about 19.7 kV / mm, it has a dielectric breakdown voltage of 5.5 kV when it is 0.28 mm, so it is suitable as a packaging material with a thickness suitable for driving atmospheric plasma. Finally, a patterned metal sheet of chrome-nickel alloy was bonded directly on the dielectric barrier layer to form a second electrode layer.

4, the first electrode layer is used as an electrode for applying a bipolar square wave voltage of 15 KHz, and the second electrode layer is used as a ground electrode to generate a total electric power The dielectric barrier discharge was driven at 110 W, which was treated with air instead of gas replacement packaging using specific gases.

(4) Microbial analysis

To 3 g of plasma-treated cheese, add 27 mL of 0.85% sterilized saline, homogenize for 120 seconds using a bag mixer (Model 400, Interscience, France) and dilute with decanter dilution to each medium . Microbial proliferation was counted by standard agar culture method at 37 ℃ for 2 days for bacteria and 5 days for mold at 25 ℃. The plasma-treated culture medium was counted after the plasma treatment and after culturing according to each culture condition. Microbial counts were expressed as CFU / g and CFU / mL, counting the number of colonies formed.

(5) Statistical processing

The results obtained in this experiment were analyzed by one-way analysis of variance using SAS software (ver. 9.3 SAS Institute Inc, USA) and the differences between mean values were compared using Duncan's multiple test. All experiments were performed with 3 repetitions. The mean and standard error (SEM) were shown, and the significant difference was evaluated at 5% level.

Experimental results 1. Pathogenic bacterial and fungal killer effect

The killing effect of three kinds of pathogenic bacteria and one fungus by the plasma treatment is shown in Figs. L. monocytogenes gradually decreased with 10.29 log CFU / mL plasma treatment time and became below the detection limit for 10 minutes treatment (FIG. 5). No E. coli O157: H7 microorganism was also detected at the initial value of 9.28 log CFU / mL for 5 minutes of plasma treatment (FIG. 6). In the case of S. Typhimurium , the initial value of 7.47 log CFU / mL was found to be below the detection limit in the plasma treatment for 75 seconds, which is relatively short compared with the other strains (Fig. 7). In the case of A. flavus spores, the fungal spores were not detected by plasma treatment for only 45 seconds at 3.79 log spores / mL (FIG. 8).

Studies on the control of E. coli O157: H7 and Staphylococcus aureus pathogenic bacteria using various types of plasmas have been published (Mok, C., Song, DM 2010. Food Eng . Progress . 14, 202-207; Mok, C., Lee, T. 2011. Food Eng . Progress . 15,398-403). It has been reported that the microbial kill mechanism by the plasma is sterilized by ultraviolet rays generated by the plasma discharge, the reactive active species, and the like, and the sterilizing characteristics are various depending on the electrode and the gas used for generating the plasma. According to a study by Moisan et al., Microbial death due to plasma is caused by DNA deformation on ultraviolet rays generated, release of volatile substances generated by chemical bond breakage caused by ultraviolet photons, and adsorption reaction of reactive compounds generated from plasma (Moisan, M. et al., Pure Appl . Chem . 74, 349-358). In addition, as a result of applying plasma to the nutrient cells of fungi as well as bacteria, it has been reported that the growth is inhibited and hyphae are deformed and collapsed (Avramidis G. et al., 2010. Surf . Coat . Tech . 205, S405-S408) .

Experimental results 2. The killing effect of pathogenic bacteria contaminated with cheese

The killing effects of the three pathogenic bacteria by the plasma treatment are shown in Table 1 below. L. monocytogenes decreased gradually with plasma treatment time at 6.19 log CFU / g, which was 4.14 log CFU / g for 10 min treatment and decreased by 2.05 log CFU / g for plasma. E. coli O157: H7 showed 3.06 log CFU / g at the initial value of 6.12 log CFU / g, and 3.06 log CFU / g at the plasma treatment for 10 minutes. In the case of S. Typhimurium, the detection limit was found to be below the detection limit in plasma treatment for 10 minutes at 5.75 log CFU / g.

Treatment time (min) Pathogens (Log CFU / g) Listeria monocytogenes Escherichia
coli O157: H7 Salmonella Typhimurium 0 6.19 ^a 6.12 ^a 5.75 ^a 2.5 5.59 ^b 4.78 ^b 4.71 ^b 5 4.85 ^c 3.82 ^c 3.77 ^c 10 4.14 ^d 3.06 ^d ND ^d SEM ¹ 0.089 0.032 0.020

¹ Standard errors of the mean (n = 12).

^{a- d} different letters within same column differ significantly (p <0.05).

This is due to the reduction of 8 and 2 log CFU / g of L. monocytogenes contaminated with cheese and ham by atmospheric plasma treatment (Song, H. et al., Food Microbiol . 26, 432-436) and DBD the E. coli and S. aureus contamination on cheese by means of plasma 2 log CFU / g was reduced in the research (Lee, HJ et al., J. Anim. Sci. Technol. 54, 191-198). However, as a basic research for applying to the food industry so far, there is a disadvantage in that the plasma system is very small and the processing range is limited. Therefore, the plasma packaging material of the present invention can be applied as a very attractive technology in the food industry .

The present invention has been described with reference to the preferred embodiments. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the present invention is defined by the appended claims rather than by the foregoing description, and all differences within the scope of equivalents thereof should be construed as being included in the present invention.

Claims (7)

A packaging material outer layer formed of a synthetic resin film;
A first electrode layer of an electroconductive metal thin film laminated on the outer layer;
A dielectric barrier layer stacked on the first electrode layer and being an insulator; And
And a second electrode layer of an electrically conductive metal foil laminated on the dielectric barrier layer and perforated at regular intervals so that a dielectric barrier layer is visible,
Wherein the second electrode layer is used as a ground electrode and a voltage is applied to the first electrode layer to generate a low temperature atmospheric plasma.
The food packaging material according to claim 1, further comprising an electrode protection layer disposed between the first electrode layer and the dielectric barrier layer and formed of a synthetic resin film.
The food packaging material of claim 1, wherein the electrically conductive metal is selected from the group consisting of aluminum, iron, nickel, chromium, copper, silver and gold.
The food packaging material according to claim 1, wherein the insulator is selected from the group consisting of polytetrafluoroethylene, mica, polyethylene, polystyrene, and polyester.
The food packaging material according to claim 1, wherein the voltage applied to the first electrode layer is a low frequency pulse voltage of 1 to 100 kHz having a pulse width of 10 to 200 ns.
The food packaging material according to claim 1, wherein the packaging material exhibits a sterilizing effect on food poisoning bacteria while preventing oxidation of food.
The food packaging material according to claim 6, wherein the food poisoning bacterium is Listeria monocytogenes, E. coli, Salmonella typhimurium or Aspergillus flavus.

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